The pulp irritation test is required for all dental materials which are used for restoring a dental cavity that does not perforate to the pulp. The traditional use of human and subhuman primates to evaluate the effects of restorative materials on dental pulp has been generally accepted. However, use of human subjects and primate animals has a number of limitations, such as inability to quantitate the results, limited reproducibility of the test conditions, high cost, limited availability, and ethical constrains. Efforts have been made to examine the pulp responses to materials using cultured cells; however, at present there has been no successful in vitro system which duplicates clinical observations of pulp responses to restorative materials. The objective of this proposal is to develop an in vitro, cell culture model which may be used to examine the cellular response of dental pulp to various restorative materials. Using two proposed reference materials, the efficacy and accuracy of the in vitro model will be determined by examining such variables as the thickness and surface texture of dentin, sterilization procedure, the time of restoration insertion, and the methods for evaluating cellular responses to materials. Efforts will be made to refine the sensitivity and reproducibility of the model after the feasibility of the proposal has been achieved. Although an in vitro system may not be able to restorative materials, it is believed that a simulated, in vitro working model, as proposed in this project, will be valuable for screening purposes before an in vivo usage test becomes necessary.